Actuation system

ABSTRACT

An actuation system which is operated by compressed fluid at a pressure determined by a pressure regulator responsive to the highest load signal acting on the system to vary the pressure in accordance with the actual output demands.

United States Patent Robert M. Salemka Portage, Mich.

Mar. 12, 1969 July 13, 1971 Pneumo Dynamics Corporation Cleveland, Ohio Inventor Appl. No. Filed Patented Assignee ACTUATION SYSTEM 17 Claims, 5 Drawing Figs.

US. Cl

FlSb 1/02 Field 0! Search 60/51, 57, 57 R, 57 T, 62; 91/6, 59, 361

References Cited UNITED STATES PATENTS 3/1958 Govan et al 60/51 2/1941 Griffith et al. 60/51 UX 5/1960 Sturgis 60/51 X 5/1961 MacMillin 60/52 HE 7/1946 Doll 60/54.5 HA 5/1951 Patterson 70/51 X Primary Examiner-Edgar W. Geoghegan Attorney-Stephen M. Mihaly ABSTRACT: An actuation system which is operated by compressed fluid at a pressure determined by a pressure regulator responsive to the highest load signal acting on the system to vary the pressure in accordance with the actual output demands.

ionouzf MOTOR PATENTED JUL] 31971 SHEET 1 BF 2 INVENTOR ROBERT M. SAL [MK/l ATTORNEY PATENTEU JUL 1 3 \QYI SHEET 2 [IF 2 GAS/OIL PUMP INVENTOR ROBERT M. SALEM/(A ATTORNEY ACTUATION SYSTEM BACKGROUND OF THE INVENTION This invention relates to a self-contained pressure actuation system in which the system pressure readily adapts itself tothe actual load demands placed on the system to provide substantially improved performance over previous known nonadaptive constant pressure actuation systems.

Pressure actuation systems for space vehicles and the like are oftentimes operated by a compressed fluid such as helium at constant pressure which may drive a hydraulic pump for supplying the required pressure to actuate one or more output shafts. For reliability, the reservoir for the compressed fluid must be sufficiently large to provide fluid flow at pressures equal to the peak design load during the entire duty cycle, or otherwise the system may stall out. However, during certain portions ofthe duty cycle, the pressure required to accomplish the work to be done may be much less than required at peak design load, resulting in a substantial waste in fluid and greatly reduced efficiency of the system. As a consequence, the size and weight of the reservoir often become limiting factors which exclude the system from being used in many aerospace and other such applications.

Moreover, even where the weight and size of the reservoir are not critical, previous known constant-pressure systems do not readily adapt themselves to unusual duty cycles and cannot tolerate loads in excess of the design loads without stalling out, whereby their use is limited only to those applications where the requirements are generally predictable or where a large safety factor can be incorporated in the system.

SUMMARY OF THE INVENTION With the foregoing in mind, it is a principal object of this invention to provide a pressure actuation system of an entirely different nature which is capable of varying the supply pressure to meet variations in output demands, thus minimizing the amount of supply pressure that must be stored in the system, and permitting a much more compact and lightweight reservoir to be used than in previous known systems.

Another object is to provide. such a pressure actuation system which is able to readily adapt itself to unusual duty cycles, making it suitable for a wide variety of uses.

Still another object is to provide such a pressure actuation system which is more efficient than previous known systems and will tolerate loads well in excess of the design load without stalling.

These and other objects of the present invention are achieved by providing a pressure regulator for.the compressed actuating fluid which is responsive to the highest load signal produced by the system to vary the actuating pressure in accordance with the actual output demands.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the fol lowing description and the annexed drawings setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principles of the inventionmay be employed.

BRIEF DESCRIPTION OF THE DRAWINGS In the annexed drawings:

FIG. I is a side elevation view of a preferred form of actuation system in accordance with this invention with portions of the housing broken away to show certain ofthe system components;

FIGS. 2 and 3 are end elevation views-ofthe actuation system-as seen from the right and left ends of FIG. 1, respectively;

FIG. 4 is a schematic diagram of the system of FIG. 1 to illustrate more clearly the manner in which the various coniponents of the system are operatively connected together; and

which controls the setting of the pressure regulator in accordance with the highest load signal of the system.

DESCRIPTION OF THE PREFERRED EMBODIMENT The actuation system I illustrated by way of example in FIGS. I through 3 of the drawing generally comprises a tubular housing 2 in which are suitably mounted a plurality of cir cumferentially spaced actuators 3 through 6 adapted to drive the associated output shafts 7 through 10 which project radially outwardly through the tubular housing 2. Hydraulic fluid is supplied to the actuators 3 through 6 by a gas/oil pump 11 driven by compressed gas supplied through a pressure regulator 12 from a pair of storage tanks 13. The setting for the pressure regulator 12 is controlled by a peak load selector 14 in a manner to be subsequently fully explained. Oil for the pump 11 may be stored in a reservoir 15 from whence it is pumped into an accumulator l6 for providing an instantaneous source of high-pressure oil to a plurality of servo valves 17 through 20, one for each actuator 3 through 6.

For a more complete understanding of the details of construction and operation of the actuation system 1, reference may be had to FIG. 4, which schematically shows the various components of the system and the manner in which they are interconnected together. Since the plural gas storage tanks 13, actuators 3 through 6, output shafts 7 through 10, and servo valves 17 through 20 are all duplic'ative, and the exact number may be varied in accordance with the requirements of a particular application, only one of each is shown for purposes of simplification.

The gas storage tank 13 may have a diaphragm seal 25 at its open end 26 which may be broken upon command by a squib valve 27. When fired, the squib valve 27 drives a cutter 28 through the diaphragm seal 25. The high-pressure gas contained in the storage tank 13, which may be helium or other suitable gas, is throttled across the pressure regulator 12 to obtain a regulated outlet pressure that may be varied as for example between l70 and 530 p.s.i.g. depending on the actuator load. The lower regulated'pressure level is controlled by a preload tension spring 29 which is'connected to'the ste'rn'30 of the pressure regulator valve 31 tending to pull the same downwardly against its seat'32 in opposition to the pressure in the storage tank 13 acting on the pressure regulator valve 31. An increase in the regulated pressure occurs as the pressure in the passage 33 increases in accordance with increased work demands at the output shafts 7'through" 10 in a manner to be subsequently explained, to urge the piston 34a contained in bore 34'upwardly so that spring 29 a presses upwardly against stem 30 with increased pressure. The upper limit of regulated pressure is controlled by a travel stop on the-upper-end ofbore 34.

From-the pressure regulator 12 the'regulated gas pressure enters the gas/oil pump 11 via the conduit 35- and branch conduit 36 to drive the pump thus creating a nominal pressure rise of desirably about-6.4:l in theoiIwhichis drawn from the reservoir 15 through the conduit 37 and supplied to the accumulator 16 through the conduit 38. The gas is exhausted from the pump 11 through an outlet port 39.

The oil reservoir 15 desirably consists ofa chamber 40 hav* ing a piston 41 contained therein, biased by a spring 42 to compress the oil to a slight extent, and having a rod 43 extending upwardly into a smaller chamber-44 ported at 45 to the conduit 35. Since the area of the rod 43 is lessthan that of the piston 41, this results in a reduction in the pressure acting on the oil in the reservoir 15 proportional to the relative areas of the piston-41 and rod 43, which in this instance is 6: l. Theaccumulator 16 is of similar construction, including a piston 46 contained in a large chamber 47 and having a rod 48 projecting therefrom into a smaller diameter chamber 49. However, the larger chamber 47 rather than the smaller'chamber'49 is ported at 50 to the regulated pressureconduit 35, thereby providing an increase in pressure in the accumulator 16 prowhich'in this case is again 6: l. A fill and bleed port 60 may be provided for charging the system with oil as required.

The gas/oil pump 11 supplies the majority of the steady state flow to the servo valves 17 through 20 via the branch conduits 51, 52, and 53, whereas the accumulator 26 provides an instantaneous source of high-pressure oil to such servo valves and smoothes out the pressure pulsations of the pump. Only the servo valve 17 is shown in FIG. 4 since they may all be of the same general construction and accordingly a description of one will be sufficient. As illustrated, the servo valve 17 is in the form of a four-way, single-stage closed center spool valve 54 coupled directly to an electromagnetic torque motor 55. Current proportional to the error between the command angular position of the output shaft 7 and its actual position will cause the torque motor 55 to drive the spool valve 54 to a position permitting high-pressure oil in the conduit 51 to enter one of the motor passages 56 or 57 and connect the other motor passage to the reservoir 15 through a return conduit 58 common to all of the servo valves 17 through 20. Such motor passages 56 and 57 are connected to opposite ends of the actuator 3 for driving the actuator piston 60 in one direction or the other to rotate the output shaft 7 through a suitable linkage 61 having a lost-motion connection 62 with the actuator piston. The output shaft 7 in turn drives a feedback potentiometer 63 operatively connected to the torque motor 55, whereby when the actual position of the output shaft matches the command position, the torque motor current signal will drop to zero and the system will come to rest.

Actuator torque loads on any or all of the output shafts 7 through are detected by the peak load selector 14, which selects the highest load signal of all of the actuators 3 through 6 and feeds that signal back to the passage 33 leading to the pressure regulator 12. As best seen in FIG. 5, the peak load selector 14 is a simple ball logic circuit consisting of a first set of check valves 65, one for each actuator, disposed in passages 66 communicating with opposite ends of the actuators 3 through 6 for transmitting the highest pressure from each actuator to additional passages 67, one for each pair of actuators. The passages 67 contain additional check valves 68 which select the highest pressure from each pair of actuators and transmit that pressure to still another passage 69 containing yet another check valve 70, and so on until the highest load pressure that is present among all of the actuators is selected. That pressure is in turn fed to the passage 33 to regulate the setting of the pressure regulator valve 31, thus to regu late the hydraulic pressure for the entire system in accordance with the highest load pressure. Accordingly, the stall torque capacity of the system increases or decreases with the actual load on the system. For example, if the actual demand on the system drops during a relatively inactive part of the work cycle, the regulated pressure will also drop, resulting in a substantial savings in the amount of gas used during that period. Then as the highest load on the output shafts 7 through 10 increases, the regulated pressure will automatically increase as required to suit the workload. This is true whether the duty cycle is as expected, or unexpected, since the system will readily adjust to the load demands, and will even tolerate loads well in excess of the original design loads without stalling out. Moreover, if any portion of the duty cycle is found to be less or more demanding than expected, the actuating pressure lower limit can readily be adjusted up or down by varying the tension of the preload spring 29 to most efficiently accomplish the work required of the system.

Because the gas pressure varies in accordance with work demands, rather than remains constant as in previous known devices, the energy that must be stored in the system to perform the totalwork required by the system over the entire duty cycle is minimized, thus permitting the use of a much smaller reservoir to store the gas for increased efficiency in packaging, which makes the system available for use in applications where space and weight limitations might have otherwise excluded it.

To permit checking out of the system after installation, a checkout and gas fill port 71 may be provided through which high-pressure external gas may be supplied to the regulated pressure conduit 35. In this manner, every portion of the system except for the squib valve 27 and rupture diaphragm 25 may be checked out without replacement.

Other modes of applying the principles of the invention may be employed, change being made as regards the details described, provided the features stated in any of the following claims or the equivalent ofsuch be employed.

I, therefore, particularly point out and distinctly claim as my invention:

1. An actuation system comprising a plurality of output shafts, a plurality of fluid pressure-actuated means for driving said output shafts, a reservoir for supplying fluid pressure, mean for varying the fluid pressure supplied by said reservoir to meet variations in the demands placed on one of said output shafts comprising a pressure regulator responsive to the load signal applied to one of said output shafts to meet the demands placed thereon, and means for selecting the highest load signal applied to said output shafts and feeding such highest load signal to said pressure regulator for regulating the fluid pressure for all of the output shafts in accordance with the highest load pressure.

2. The actuation system of claim 1 wherein said last-mentioned means comprises a fluid logic circuit which compares the load pressure signals applied to each of said output shafts and selects and feeds the highest load signal to said pressure regulator as aforesaid.

3. A pressure actuation system comprising an output shaft, an actuator for controlling the movement of said output shaft, a gas/oil pump for supplying hydraulic fluid to said actuator to drive the same, a gas reservoir for supplying compressed gas to said gas/oil pump for actuating the same, and means for varying the pressure at which such compressed gas is supplied by said reservoir to said gas/oil pump in accordance with variations in the actual work demands placed on said output shaft.

4. The actuation system of claim 3 further comprising an oil reservoir for supplying hydraulic fluid to said gas/oil pump, the hydraulic fluid in said oil reservoir being maintained under pressure.

5. The actuation system of claim 4 further comprising an accumulator for storing the compressed hydraulic fluid, the hydraulic fluid in said accumulator being maintained under pressure.

6. The actuation system of claim 3 further comprising a servo valve for controlling the flow of hydraulic fluid to said actuator, an electromagnetic torque motor operatively connected to said servo valve for driving the same, means for supplying a command signal to actuate said torque motor, and a feedback potentiometer driven by said output shaft and operatively connected to said torque motor, whereby when the actual position of the output shaft matches the command position, said torque motor will stop.

7. The actuation system of claim 3 wherein said means for varying the pressure of the compressed gas comprises a pressure regulator for throttling the compressed gas, and means for directing the load signal applied to said output shaft against said pressure regulator to vary the setting of said pressure regulator.

8. The actuation system of claim 7 further comprising means acting on said pressure regulator for controlling the lower level of such regulated gas pressure.

9. The actuation system of claim 3 wherein there are a plurality of said output shafts driven by a corresponding number of actuators operatively connected to said oil/gas pump, said means for varying the pressure of the compressed gas comprising a pressure regulator for throttling the compressed gas, and means for selecting the highest load signal applied to all of said output shafts and feeding such highest load signal to said pressure regulator to vary the setting thereof.

10. The actuation system of claim 9 wherein said last-mentioned means comprises a fluid logic circuit which compares the load signals supplied to all of said output shafts and selects the highest load signal which is fed to said pressure regulator as aforesaid.

11. The actuation system of claim 3 further comprising a diaphragm seal for initially sealing said gas reservoir, and a squib valve having a cutter which when fired breaks said seal.

12. The actuation system of claim 11 further comprising porting means operatively connected to said system for permitting high-pressure external gas to be supplied to said system for checking system performance without having to break said seal.

13. The actuation system of claim 4 further comprising a piston disposed in said oil reservoir above the hydraulic fluid, and spring means for biasing said piston into contact with the hydraulic fluid to maintain such hydraulic fluid under pressure.

14. The actuation system of claim 4 further comprising a piston disposed in said oil reservoir above the hydraulic fluid, and a smaller diameter rod extending upwardly from said piston which is acted upon by the gas from said gas reservoir for placing the hydraulic fluid in said oil reservoir under pressure.

15. The actuation system of claim 3 further comprising an accumulator for storing the compressed hydraulic fluid, a rod disposed in said accumulator above the hydraulic fluid, and a larger diameter piston attached to the other end of said rod acted upon by the gas from said gas reservoir for placing the hydraulic fluid in said accumulator under pressure.

16. An actuation system comprising an output shaft, fluid pressure actuated means for driving said output shaft, a pump for supplying fluid pressure to operate said fluid pressure-actuated means, and means for increasing and decreasing the rate of operation of said pump to increase and decrease the fluid pressure supplied to said fluid pressure-actuated means in accordance with increased and decreased output loads placed on said output shaft to provide the required pressure to overcome such loads and drive said output shaft.

17. The actuation system of claim 16 wherein said pump is gas operated, and said means for increasing and decreasing the operation of said pump comprises pressure regulator means for supplying gas at different pressures to said pump in proportion to the actual work demands placed on said output shaft to vary the rate of operation of said pump. 

1. An actuation system comprising a plurality of output shafts, a plurality of fluid pressure-actuated means for driving said output shafts, a reservoir for supplying fluid pressure, mean for varying the fluid pressure supplied by said reservoir to meet variations in the demands placed on one of said output shafts comprising a pressure regulator responsive to the load signal applied to one of said output shafts to meet the demands placed thereon, and means for selecting the highest load signal applied to said output shafts and feeding such highest load signal to said pressure regulator for regulating the fluid pressure for all of the output shafts in accordance with the highest load pressure.
 2. The actuation system of claim 1 wherein said last-mentioned means comprises a fluid logic circuit which compares the load pressure signals applied to each of said output shafts and selects and feeds the highest load signal to said pressure regulator as aforesaid.
 3. A pressure actuation system comprising an output shaft, an actuator for controlling the movement of said output shaft, a gas/oil pump for supplying hydraulic fluid to said actuator to drive the same, a gas reservoir for supplying compressed gas to said gas/oil pump for actuating the same, and means for varying the pressure at which such compressed gas is supplied by said reservoir to said gas/oil pump in accordance with variations in the actual work demands placed on said output shaft.
 4. The actuation system of claim 3 further comprising an oil reservoir for supplying hydraulic fluid to said gas/oil pump, the hydraulic fluid in said oil reservoir being maintained under pressure.
 5. The actuation system of claim 4 further comprising an accumulator for storing the compressed hydraulic fluid, the hydraulic fluid in said accumulator being maintained under pressure.
 6. The actuation system of claim 3 further comprising a servo valve for controlling the flow of hydraulic fluid to said actuator, an electromagnetic torque motor operatively connected to said servo valve for driving the same, means for supplying a command signal to actuate said torque motor, and a feedback potentiometer driven by said output shaft and operatively connecTed to said torque motor, whereby when the actual position of the output shaft matches the command position, said torque motor will stop.
 7. The actuation system of claim 3 wherein said means for varying the pressure of the compressed gas comprises a pressure regulator for throttling the compressed gas, and means for directing the load signal applied to said output shaft against said pressure regulator to vary the setting of said pressure regulator.
 8. The actuation system of claim 7 further comprising means acting on said pressure regulator for controlling the lower level of such regulated gas pressure.
 9. The actuation system of claim 3 wherein there are a plurality of said output shafts driven by a corresponding number of actuators operatively connected to said oil/gas pump, said means for varying the pressure of the compressed gas comprising a pressure regulator for throttling the compressed gas, and means for selecting the highest load signal applied to all of said output shafts and feeding such highest load signal to said pressure regulator to vary the setting thereof.
 10. The actuation system of claim 9 wherein said last-mentioned means comprises a fluid logic circuit which compares the load signals supplied to all of said output shafts and selects the highest load signal which is fed to said pressure regulator as aforesaid.
 11. The actuation system of claim 3 further comprising a diaphragm seal for initially sealing said gas reservoir, and a squib valve having a cutter which when fired breaks said seal.
 12. The actuation system of claim 11 further comprising porting means operatively connected to said system for permitting high-pressure external gas to be supplied to said system for checking system performance without having to break said seal.
 13. The actuation system of claim 4 further comprising a piston disposed in said oil reservoir above the hydraulic fluid, and spring means for biasing said piston into contact with the hydraulic fluid to maintain such hydraulic fluid under pressure.
 14. The actuation system of claim 4 further comprising a piston disposed in said oil reservoir above the hydraulic fluid, and a smaller diameter rod extending upwardly from said piston which is acted upon by the gas from said gas reservoir for placing the hydraulic fluid in said oil reservoir under pressure.
 15. The actuation system of claim 3 further comprising an accumulator for storing the compressed hydraulic fluid, a rod disposed in said accumulator above the hydraulic fluid, and a larger diameter piston attached to the other end of said rod acted upon by the gas from said gas reservoir for placing the hydraulic fluid in said accumulator under pressure.
 16. An actuation system comprising an output shaft, fluid pressure actuated means for driving said output shaft, a pump for supplying fluid pressure to operate said fluid pressure-actuated means, and means for increasing and decreasing the rate of operation of said pump to increase and decrease the fluid pressure supplied to said fluid pressure-actuated means in accordance with increased and decreased output loads placed on said output shaft to provide the required pressure to overcome such loads and drive said output shaft.
 17. The actuation system of claim 16 wherein said pump is gas operated, and said means for increasing and decreasing the operation of said pump comprises pressure regulator means for supplying gas at different pressures to said pump in proportion to the actual work demands placed on said output shaft to vary the rate of operation of said pump. 